1. Field of the Invention
The present invention relates to an upright piano type action including an action for an upright piano and an action of the same type as the action for an upright piano.
2. Description of the Related Art
On the market, there are a multiplicity of electronic keyboard musical instruments which generate musical tones that are close to those of a piano (acoustic piano). In many cases, such electronic keyboard instruments are used as a substitute for a piano. By improvements made to the electronic keyboard instruments for better sound quality, musical tones generated by the electronic keyboard instruments are quite close to those of pianos. As a result, not only the sound quality but also an action which is close to that of a piano is demanded of electronic keyboard instruments.
As for action of piano, there are differences in functions and touch between grand pianos and upright pianos. Generally speaking, the mass of a swing member such as a hammer acts mainly as a static load when the force with which a key is depressed is small. When the force with which the key is depressed is great, however, the mass acts largely as a dynamic load, for the acceleration of the swing member increases.
In a case of an action of a grand piano, more specifically, it is respective loads of a hammer shank, a hammer and a hammer roller that act on a jack in response to a depression of a key. Furthermore, the entire action of the grand piano is light, whereas the action is designed such that the hammer is raised from a position at which the hammer is nearly horizontal with respect to a swing fulcrum to hit a string. Therefore, the action of the grand piano has a good balance between static load and dynamic load, allowing a player to clearly perceive resistance to a weak depression of a key, and preferably increasing dynamic resistance with an increase in the strength of depression of the key. That is, the action of the grand piano allows the player to perceive the touch which is rich in the feeling of mass.
In a case of an action of an upright piano, on the other hand, it is respective loads of a wippen, a butt, a hammer shank, a hammer, a catcher shank, a catcher and the like that act on a jack in response to a depression of a key as described in Japanese examined utility model publication No. 62-43349, for example. In order to prevent the total weight of these members from becoming excessively heavy, therefore, respective masses of these swing members have to be kept small. In addition, the action of the upright piano is designed such that the hammer swings in a range in which the hammer keeps almost upright to hit a string. In spite of the static load, as a result, the action of the upright piano fails to apply an adequately increased dynamic load in response to a strong depression of a key. Therefore, the action of the upright piano offers light dynamic resistance to a key-depression, providing the player with touch which is poor in the feeling of mass.
As described above, a grand piano type action is preferable as a piano action for an electronic keyboard instrument in view of player's touch. However, the grand piano type action is not suitable for an electronic keyboard instrument which is compact in size, for the grand piano type action is large in the front-to-back direction. For such a compact electronic keyboard instrument, therefore, an upright piano type action is employed.
If an action for an upright piano which provides the player with touch which is as rich in the feeling of mass as that of a grand piano is available, the quality of the upright piano will improve significantly. Therefore, an action providing such touch has been demanded of upright pianos.